Shots - Health Blog
Thu July 19, 2012
How HIV Hijacks The Immune System
Originally published on Tue July 24, 2012 5:23 pm
The road to a cure for AIDS is in sight, even if every step on the journey isn't clear yet.
One of the most promising avenues is a kind of gene therapy that would block HIV's entry into cells of the immune system. A genetic tweak could make these key cells resistant to the virus's attack.
"HIV is like a jack-in-the-box," says Sriram Subramaniam, a biophysicist at the National Cancer Institute who peers at HIV with electron microscopes.
The virus's genetic material sits inside a shell that is studded with spikes. To infect a cell, the shell has to pop open and release the virus's genes into the cell.
That's what happens when HIV bumps into T cells, the white blood cells that are the virus's prime targets.
T cells are studded with finger-like projections, including one called CCR5 that fits on HIV's spikes.
A gene therapy now being tested in people takes the CCR5 receptor out of their T cells. Without CCR5, the cells don't trigger the virus's jack-in-the-box invasion. If the virus can't get inside the cells, it can't reproduce.
A few people, mainly Caucasians, lack CCR5 because of genetic mutations. And one man who received bone marrow transplants for leukemia from a donor without CCR5 receptors has been cured of HIV/AIDS, his doctors say.
Separately, Subramaniam has found evidence that HIV hide in other places in the immune system even before it enters cells.
Using a microscopy technique to create 3-D models of cell surfaces, he and his team saw some immune cells took on flower-like shapes. HIV can hide in crevices between the large petal-like sheets.
These pools of HIV may help the virus's move around the immune system, Subramaniam tells Shots.
The virus gets a free ride as these cells move through the blood. "T cells can reach deep into these channels to pick up the HIV itself," says Subramaniam.